OBJECTIVE: To estimate the effect of prolonged vaginal distention and anal sphincter transection on contractile properties of the external anal sphincter.
METHODS: Young female virgin rats were randomly assigned to four treatment groups (sham, vaginal distention, transection of anal sphincter plus repair, or combined distention and transection plus repair). After 3 weeks, the anal sphincter complex was analyzed for twitch tension, maximal tetanic force, fatigue, and maximal responses to electrical field stimulation. Each sphincter was serially cross-sectioned and stained with hematoxylin and eosin to evaluate sphincter integrity. Statistical evaluation was performed using analysis of variance (Student-Newman-Keuls) and χ2 analysis.
RESULTS: The function of a transected and repaired anal sphincter is compromised significantly after 3 weeks. Vaginal distention alone did not alter function of the sphincter. Further, prolonged vaginal distention together with sphincter transection did not result in statistically significant differences in sphincter function compared with transection alone.
CONCLUSION: In an animal model, there is a major effect on external anal sphincter function in vitro 3 weeks after laceration with repair. Although prolonged vaginal distention had no significant effect alone and minimal adverse effects on the lacerated anal sphincter, laceration of the sphincter has major adverse effects on its morphology and function.
LEVEL OF EVIDENCE: II
In an animal model, there is major effect on external anal sphincter function in vitro 3 weeks after laceration with repair.
From the Divisions of 1Urogynecology and Reconstructive Pelvic Surgery and 3Reproductive Endocrinology, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas; and 2ProPath Laboratories, Inc., Dallas, Texas.
Supported by a research grant from The American Urogynecologic Society/June Allyson Foundation.
Corresponding author: Clifford Y. Wai, MD, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-9032; e-mail: Clifford.Wai@UTSouthwestern.edu.
Financial Disclosure The authors have no potential conflicts of interest to disclose.